Light-sensitive layer and method of making the same



Patented Apr. 29, 1941 LIGHT-SENSITIVE LAYER AND METHOD OF MAKING THE SAME Jan Hendrik de Boer, Roeloi' Jan Hendrik Alink.

and Johannes Josephus Antonius Junkers,

Eindhoven, Netherlands, asslgnors, by mesne assignments, to Hartford National Bank and Trust Company, Hartford, Conn., as trustee No Drawing. Application February 8, 1939, Se-

rial No. 255,344. 10, 1938 13 Claims.

By a light-sensitive layer capable of self-development is meant one which contains a diazonium compound, a coloring component, and if desired an alkaline-reacting substance, and with which images can be produced, after an exposure, solely by applying water to the layer. With such layers an intense color is formed at the non-exposed portions, little or no color is formed at the exposed portions, and the fixation of the image is effected without the addition of further substances.

The term coloring component is to be understood to mean a material which, in the presence of water, and if desired an alkaline-reacting substance, is capable of reacting with the diazonium compound to produce dyestufi.

One object of our invention is to provide an improved method of making such layers.

A further object is to produce light-sensitive self-developing layers which are less subject to premature development due to atmospheric conditions and handling, and are protected against abrasion.

A still further object is to increase the sharpness and detail of the prints produced on such layers.

Another object is to permit the development to be effected in a satisfactory way by applying liquid water to the layer..

Still further objects and advantages of the invention will be apparent to one skilled in the art from the following particular description.

In accordance with the invention, we sensitize a suitable carrier, for instance a strip of paper, by applying thereto a solution containing a diazonium compound, and then dry the carrier. We then place at least one of the materials required for the formation of dyestufi in suspension by mixing the same in a finely-divided state in a solution comprising a binder dissolved in a volatile liquid solvent which will not dissolve any substance required for the formation of the dyestuff. This suspension is applied to the sensitized dry carrier, and then the solvent is volatilized to form a layer containing the binder and suspended material. We may apply a coloring component, an alkaline-reacting component, or both by means of a suspension thereof.

With such light-sensitive layers, in which the binder securely holds the suspended material in place, the light used for making the exposure. acts in a very homogeneous manner with there- In the Netherlands February sult that the finished prints have very sharp de- ..tail. However, to still further improve the sharpness of the detail we prefer to employ binders which, for the light to which the diazonium compound is sensitive, have indices of refraction which are as close as possible to that of the suspended material. In cases in which a plurality of materials are suspended in the solution and have widely-differing indices of refraction, we prefer to use a binder whose index of refraction is as close as possible to the index of refraction of that suspended material which in the mixture most diffuses the light.

The layer applied by the method of the present invention is extremely well protected mechanically, for example against any rubbing or scrubbing which may occur during handling or winding into rolls, and is also protected chemically, for instance against the action of moisture of the atmosphere and handling the light-sensitive material with moist fingers.

We have found that to obtain the above advantages it is essential that the binder and the finely-divided material be applied at the same time, the finely-divided material being suspended in the solution of the binder. More particularly we have found that comparable results could not be obtained if the binder were to be first applied to the sensitized carrier and the finely-divided material then applied in a dry state, or vice versa.

In practicing the invention the selection of volatile liquid solvents and of binder materials depends upon s veral factors. For example the solvent must, of course, be volatile and must be one in which only the binder will dissolve, but in which all other substances to be used should not dissolve. The binder material should be one which, when in its solid state, is rather flexible, should be substantially transparent to the light to which the layer is sensitive, and should not discolor the carrier.

As suitable binders for carrying out the invention we may mention for example, substances such as polystyrene, the polymerisate of esters of acrylic acid, which is sold under the name Plexigum; resins, such as dammar resins and mastix; and various kinds of waxes, such as beeswax, all of these binders being soluble in a solvent suitable for each individual case. The above binder substances are particularly suitable for carrying out the invention because their indices of refraction are close to those of the suspended materials, and also because the binder layers obtained with these substances are sufllciently elastic to allow the light-sensitive material to be handled without damage.

A substance such as paraflin is unsuitable in this respect because a binder layer obtained therewith is rather brittle and must be handled with great care to avoid cracking, which makes it inconvienient for every day use. To overcome this disadvantage, we prefer to use, instead of paraffin alone, a mixture of paraffin and, for example, beeswax. As stated the binder substances should be transparent to the light to which the layer is sensitive and should not discolor the carrier.

As suitable solvents we have found that particularly good results are obtained with chlorated hydrocarbons (chloro-organic compounds), such as carbon tetrachloride (C014) and ethylene chloride (CH2CLCH2C1), because with such solvents a very stable suspension of the finelydivided material in the solution of the binder may be readily obtained. This is particularly promoted by using with these solvents as binders, the above-mentioned polystyrene or Plexigum." In some cases a mixture of binders may be very useful.

In carrying out the invention it is desirable that the suspended material be distributed as homogeneously as possible throughout the dispersion agent during the application of the suspension to the sensitized layer. For this purpose we give the binder solution a sufliciently high viscosity. As a matter of fact the thickness of the binder layer should be such that it is sufficiently permeable to water.

The term homogeneously distributed as used herein and in the claims is to be understood to mean that a distribution which has the degree of homogeneity obtainable with suspensions.

To-further increase the durability of material sensitized according to the invention, and to prevent undesirable yellowing of print produced therewith, in some cases also photochemicallyinert additional substances may be applied to the carrier. As examples of suitable materials for these purposes we might mention dried starch and a substance which with an alkali yields a hydrated oxide soluble with difficulty, for instance aluminium sulphate. The use of such substances has been described in the U. S. Patent 2,113,193 to Jan Hendrik de Boer and in the British Patent 454,814.

The suspensions of the invention may be easily applied to a carrier, for example a paper carrier, by means of a roller. By way of example, it can be mentioned that a substance producing an alkaline reaction, such as anhydrous sodium carbonate, sodium bicarbonate, quicklime and the like, a dyestufi component, such as phloroglucinol, R-salt (sodium salt of 2-hydroxynaphthaline-3.6- disulphonic acid) and the like, and an additional substance such as aluminium sulphate, dried flour of wheat and the like may be suspended in the following manner. For example, a finely-divided mixture of the above materials is mixed in a ballmill with a binder, which has been ground heforehand in a ball-mill whilst using alcohol and subsequently collected on a filter and dried. The resulting mixture is dispersed in a carbon tetrachloride solvent by shaking, in a proportion of, for example, 100 grams of the mixture to 1 litre of solvent.

Very good results have been obtained by us by treating a paper carrier with a solution containing 24 g. of p-benzyl-ethylaminobenzenediazoniumsulfate [1)(CeH5CH2) (C2Hs) NCsH4NaSO4I-I], 12 g. of tartaric acid [HOOC(CHOH)2COOH] and 10 g. of oxalic acid (COOHCOOH.2H2O) in 1 liter water, whereupon the paper is dried.

The suspension with which the dried sensitized paper is treated contains 1.5 g. of phloroglucinol [CaH3(OH)a.2H2O], 3.4 g.-of anhydrous-sodiumcarbonate (NazCOz) 4.4 g. of borax (Na2B40'L10H20) which substances are suspended in a finely-divided state in a solution of 40 g. of polystyrene and 5 g. of dammar (e. g. cellodammarresin) in 1 liter of trichloroethylene (CHCl=CCl2).

The anhydrous sodium carbonate and borax are ground separately or together in a ball mill in the presence of ethylalcohol, after which the alcohol is removed by filtering and drying. The phloroglucinol is ground in the same manner with trichloroethylene. Then follows the suspending operation of the above mixture of substances in the binder solution, which operation too is carried out in a ball mill.

The suspension so obtained is applied in a thin layer on to the paper by means of a pair of rollers, whereupon the solvent is evaporated under the application of moderate heating. The paper is then ready for use.

After exposing under a drawing the print is developed by applying a thin film of water e. g. by treating the surface of the paper with a moist stop of cotton-wool. The print has excellent black lines on a white ground.

Additional substances as aluminiumsulfate and the like can be used with advantage when the presence of a larger quantity of alkaline substances is desired.

Although the invention has been described in detail with respect to particular preferred examples, we do not desire to be limited thereto because various changes and modifications will present themselves to those skilled in this art.

What we claim is:

1. In the manufacture of a light-sensitive layer capable of being developed solely by the application of water, the steps of sensitizing a carrier with a diazonium compound capable of reactingwith a coloring component in the presence of suf-- ficient water and if desired an alkaline-reacting component to form coloring matter, suspending at least one of said components in a finely-divided state in a solution of a binder dissolved in a volatile solvent incapable of dissolving any of the materials required for the formation of coloring matter, coating the dried sensitized carrier with the suspension, and volatilizing the solvent.

2. In the manufacture of a light-sensitive layer containing a diazonium compound and a coloring component capable of reactin in the presence of an alkaline-reacting substance and water to produce coloring matter, the steps of sensitizing a carrier with the diazonium compound, suspending the coloring component in a finely-divided state in a solution of a binder dissolved in a vola tile solvent incapable of dissolving any of the materials required for the formation of coloring matter, coating the dried sensitized carrier with the suspension, and volatilizing the solvent.

3. In the manufacture of a light-sensitive material from a diazonium compound and a coloring component capable of reacting in the presence of an alkaline-reacting substance. and water to produce coloring matter, the steps of sensitizing a carrier by applying a solution of the diazonium compound thereto, suspending both the coloring component and the alkaline-reacting substance in their finely-divided state in a solution of a binder dissolved in a volatile solvent incapable of dissolving any of the materials required for the formation of coloring matter, coating the dried sensitized carrier with the suspension, and volatilizing the solvent.

4. In the manufacture of a light-sensitive material from a diazonium compound and a coloring component capable of reacting in the presence of an alkaline-reacting substance and water to produce coloring matter,'the steps of sensitizing a carrier by applying a solution of the diazonium compound thereto, suspending in a solution of a binder dissolved in a volatile solvent incapable of dissolving any of the materials required for the formation of coloring matter the coloring component in its finely-divided state and a finely-divided additional material, coating the dried sensitized carrier with the suspension, and volatilizing the solvent.

5. In the manufacture of a. light-sensitive material from a diazonium compound and a coloring component capable of reacting in the presence of an alkaline-reacting substance and water to produce coloring matter, the steps of sensitizing a carrier by applying a solution of the diazonium compound thereto, suspending in a finely-divided state in a solution of a binder dissolved in a volatile solvent incapable of dissolving any of .the materials required for the formation of coloring matter the coloring component and a substance with which an alkali yields a difiicultly-soluble hydrated oxide, coating the dried sensitized carrier with the suspension, and volatilizing the solvent.

6. A light-sensitive material comprising a carrier, a light-sensitive layer supported by said carrier and including a diazonium compound, a coloring component capable of reacting with said ,diazonium compound in the presence of an alkater to produce dyestuii, and a, layer of a binder adhering to the carrier and being transparentto the light to which the diazonium compound is sensitive and containing homogeneously-distributed the coloring component in a finely-divided state, said binder having an index of refraction substantially equal to that of the coloring component for the light to which the diazonium compound is sensitive.

8. In the production of images the steps of sensitizing a carrier with a diazonium compound capable of reacting with a coloring component in the presence of an alkaline-reacting component and suilicient water to form coloring matter, suspending one of said components in a finelydivided state in a solution of a binder dissolved in a volatile solvent incapable of dissolving any of the materials required for the formation of coloring matter, applying the suspension to the dried sensitized carrier, volatilizing the solvent,

exposing the resulting layer to aotinic light, and applying liquid water to the layer to develop the images.

9. A light-sensitive material made by the method of claim 1.

10. A light-sensitive method of claim 2.

11. A light-sensitive method of claim 4.

12. A light-sensitive method of claim 5.

13. A light-sensitive material, comprising a paper carrier, a light-sensitive layer supported by said carrier and including a diazonium compound and a coloring component capable of reacting in the presence of an alkaline-reacting component and suflicient water to produce dyestuif, and a layer of a binder adhering to said carrier and being transparent to the light to which the diazonium compound is sensitive, said coloring component being in a finely-divided state and homogeneously distributed throughout said latter layer, said coloring component being readily removable from the carrier by agitating the mamaterial made by the material made by the material made by the terial in a solvent in which the binder is soluble and the coloring component isinsoluble.

JAN HENDRIK DE BOER. ROELOF JAN HENDRIK ALINK. J OHANNES J OSEPHUS ANTONTUS J ON'KERS. 

